DaWei

That's the OP's call. He said "short", not "looks short." Abstraction has its uses. As a means of programmer productivity at the expense of performance, I think this one has already failed.

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Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Arevos

I disagree. Hiding code away within black box is exactly what object orientation is all about. It's unlikely this solution will affect the program significantly in terms of efficiency, and from the outside it's very concise.

That said, I think the solution is silly, but for reasons different to your own, DaWei. It seems to me as if this:
Is less understandable than this:
Because you're overriding the subtraction operator to do something that isn't immediately obvious. You'd have to keep track of all your Percent objects, or not assign them to any references, otherwise things could get confusing.

Multiplication is well understood by any programmer, and multiplying by 0.8 should instantly be recognisable as a reduction of 20%. Wrapping this up in a class just makes it harder to figure out what's going on.

ptmcg

Just a couple more examples:


I still think this is rather pretty, the kind of thing that DSL's are made of. Imagine applying this same technique (emulating numeric types using _add_, _radd_, etc.) to applications such as:

• adding resistors in a network
• adding temperature of various quantities of water
• adding vectors
• adding physical bodies (with gravity, momentum) to a dynamic model

Yet I can certainly sympathize with the maintainer who, trying to debug the above code later wonders, "where the hell do they calculate the markup?".

Still, here is what the OP started with:

Of course, this is probably the simplest and most direct implementation of subtracting 5% of something from something else. Why was the OP asking the question in the first place? The Percent class illustrates an atypical object capability provided by Python, to be able to define an object that can take additional information from its arithmetic context to modify its behavior. With Percent, the OP can define
completely independently from what the tolerance is to be calculated on, and then later apply it to Energy using
or even just

So is this Percent class silly overkill for something so mundane as calculating a percentage? Perhaps. But I find Python's numeric type emulation capabilities to be quite interesting, and it seemed a decent fit and a simple example to the OP's question.

DaWei

I disagree. Object orientation is about building things as objects. The encapsulation may be used to protect parts of the object from unintended use, if one wants to call that hiding. Don't attach a spring to the butterfly valve in my carburetor in order to make a gauge showing how much the accelerator is depressed. Find another way or ask me to expose something suitable. Similarly, enclosing a carburetor in a spherical rubber case is a silly, though perhaps interesting, way to make a basketball.

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Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code.
Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Arevos

That's essentially what I was angling toward. OO restricts and hides information, and as far as I'm aware, this is the only difference between OO and procedural languages.

Unless you consider OO to be more a state of mind, rather than an syntactical attribute of a programming language?

DaWei

I consider OO to be a design methodology that far predates its 'discovery' in the software arena. It is far more than a syntactical attribute in those areas. MEs and hardware designers would probably be surprised to discover that it's considered abstruse.

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Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

kurt

Thanks, ptmcg, Arevos, DaWei and everyone for your feedback.

As I just started learning Python for work, I was wondering if Python has special utilities or functions that can perform what I posted previously, albeit it is already very short and simple.

The examples given are interesting and I thank you all for it.

Your different views on OOP (well, from a different perspective, at least) is thought provoking, and it's really beneficial for a fresh graduate like me.

Thanks, everyone.

free-zombie

"%" can be expressed with <b>e-2</b>.

Sane

This thread made me smile. Only on a programming forum will you see people carefully rip apart and analyze something as simple as calculating a percentage.

Thanks for the laugh guys.

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